The invention relates to a tool holding system for automatic tool changing in a machine tool, stamping machine or other such machine, in which the machine has a spindle which has in its free end a gripping means in the form of a sleeve which can be inserted and removed by a tool changing system, a draw rod which actuates the sleeve by axial displacement being carried in the spindle, and the tool having at its spindle end a tool holding head having a hollow centering taper of inverted frustum cane shape which, in order to clamp the tool against the spindle, can be engaged by a conical inside surface of the sleeve when it is in its chucking position.
Machine tools with tool holding systems of the kind described are disclosed, for example, in EP No. 01 01 917 B1, DE No. 32 30 051 A1 and EP No. 01 62 924 A2, and serve for the purpose of automatically performing repetitive machining processes rapidly and with great accuracy. In these machines it is common practice to grip the tools or tool holders by means of a tapered or conical shank which is axially drawn or forced into a matching socket in the spindle. The tool changing system in this case performs both a movement substantially perpendicular to the spindle axis to bring the tool up from the side or return it back to the side, as well as a relatively long axial movement for the introduction of the tapered shank into the spindle or bring the shank out of the spindle relative to the latter.
It is disadvantageous in the known machine tools and tool holding systems that, on the one hand, the relatively long course that has to be traveled by the tool in two dimensions greatly complicates the mechanism of the tool changing system, and that, on the other hand, covering this distance when changing tools takes considerable time, inasmuch as the axial movement has to be performed twice, namely once in the removal of the tool and once in the introduction of the next tool. Another disadvantage in known machines is that even relatively small differences in the diameter of the tapered shank of the tool and in the tapered bore in the spindle result in relatively great axial inaccuracies in length and level on account of the augmentation due to conicity.
The problem is therefore to create a tool holding system of the kind described above, by which a more rapid tool change will be made possible and in which a great accuracy of the axial position of the tool will be assured.